Process of making arsenate of lead.



' obtained UNITED STATES T OFFICE,

GEORGE R. RICHES AND WILLIAM C. PIVER, OF HOBOKEN, NE'W'JERSEY.

PROCESS OF MAKING ARSENATE 0F LEAD.

No Drawing.

To all whom it may concern Be it known that we, GEonon R. RICHES, a subject of the King of Great Britain, and WILLIAM C. PIVER, a citizen of the United States, and residents of Hoboken, county of Hudson, and State of New Jersey, have invented certain new and useful Improvements in Processes of Making Arsenate of Lead, of which the following is a specification.

This invention relates to an improved method for the preparation of arsenate of lead. In carrying out our methodanormal lead salt, such aslead nitrate, is caused to react in water with lead oXid and the basic lead salt thus produced is caused to react with arsenic acid.

e recognize that this type of reaction is not broadly new, but as commonly carried out it has been characterized by the disadvantages of great length'of time for completion of thereactio'n and of coarseness of the lead arsenate upon precipitation, the lead arsena-te often assuming a granular form which akes it unfit 'for convenient ap 1ication t various uses, such as an insecticide.

he present invention comprises certain improvements, as will be hereafterset forth, in the carrying out of this type ofzreaction whereby the Iength'of time necessary for the reaction of given uantities' to be completed is greatly lessene and a productobtaiined wh ch has a finely divided physical'appearance,'r equiring no grind ng. p

In carryin out the invention we make use of straight c emical reactions troduced) our advantageous results being generally by the temperature maintained and by the method employed in intr0- ducing the arsenic acid, certain other features also contributin -to the advantageous nature of our method, as will be pointed out.

We have found thatito make a batch of material the following proportions andmode of procedure are correct: v,

In a tank of suitable size, we add900 gallons of lead nitrate solution of specific gravity 1.02, and to this is added 1000 lbs. of lead oxid (htharge), andth tem erature ofthe mixture is maintained at 8 degreesto degrees centigradeg To this-mile enough arsenicjacjid to convert the basic lead nitrate into-emanate unload, he arsenic acid is of ttbdtiliegfdflglfis ture is added Specification of Letters Patent.

reaction, reacts u on some 0 no catalyzer or material foreign to-the reactlon being m and contains some nitric acid incidental Patented Mar. 4, 1919. Application filed February 3, 1917. Serial No. 146,827.

arsenic acid is led into the tank through one inch pipes and mixed with the solution.

We have found that by adding the arsenic acid subsequently nitrate and lead oxid and gradually (which is here accomplished by leading the arsenic acid into the tank through a comparatively small pipe), the time necessary for the complete reaction to take lace is greatly shortened, while we also believe that the comparatively slow adding of the arsenic acid aids in the recipitation of the lead arsenate in a finely ivided form.

This converts the lead compound into arsenate of lead immediately, so that when the arsenic acid has all been added, the insoluble lead arsenate is ready to be filtered off and utilized.

The reactions which take place are as fol The excess nitric acid formin in the final v the excess lead oxid to form cad nitrate:

Thiszlast reactionfi'is made use of and calamount o'fflead oxid first -inculated ior the troduced. The exces of lead oxid takes care of the nitricacidformed in thexreantion of the arsenic acid with redissolved finally and the product ,of' this reaction, lead nitrate, is used over again, after filtration ofthe lead arsenate, to be used in the next batch of material.

The finenesso the tribute to the temperature of the solutions Whilethe reaction is the tendency ofthe thelead arsenate' upon its immediate formation. 'We have noticed actions of this nature happening in such cases as-the precipitations of arsenic, antilnon and tin, as sulfids; es ecially the tin sul d. f If the solu tion of in: is on the yer the hydrogen sulfid wi]. precipitate the, tin su'ljid, but'lupon the discontinuance of the the basic lead nitrate, so that the lead arsenate ust formed is not lead arsenate, we at of being too acid,

to the mixing of the lead I 10b tak ng place, and also nitric acid; to dissolve stream of-hydrogen sulfid, thc tini nnlfid until the acid conditions of the bath adjust tllBll'lSBlVGS by the decom Josition of small amounts of the tin sulfids y the acid. The remaining sulfid precipitate remains suspended as minute particles.

The arsenate of lead exhibits the same phenomena, since when the nitric acid becomes neutralized by the lead oxid, the arsenate is left in this extremely finely divided condition.

What we claim is 1. The process of making arsenate of lead which consists in producing a solution of a basic lead salt in water and subsequently adding arsenic acid thereto radually while maintaining the mixture slig itly Warm.

2. The processof making arsenate of lead which consists in first mixing lead oxid and a normal salt of lead in water to produce a basic lead salt and subsequently adding thereto arsenic acid gradually while maintainin the mixture slightly warm.

3. l he process of making avery finely divided amorphous arsenate of lead upon precipitation which consists in first heating a mixture of lead oxid and a normal lead salt in water from degrees to degrees centigrade until a solution of a basic lead salt is obtained and subsequently introducing arsenic acid to such mixture.

4. The process of making arsenate of lead which consists in first reacting between lead oxid and lead nitrate in water to produce basic lead nitrate, and subsequently adding arsenic acid thereto, the temperature being maintained during the entire series of reactions at from 30 to 35 degrees centigrade.

5. Theprocess of making arsenate'of lead which consists in first mixin an excess of lead oxidand a normal salt 0 a lead in water at a temperature of 30 to 35 degrees centigr-ade'to produce a basic lead salt, and subsequently adding arsenic acid thereto, the excess oflead oxid being su cientto neutralize the acid freed by the reaction of the basic lead salt and arsenic acid and by its combination with said acid reproducing a iliesjired quantity of the said normal salt of 6. The process of making arsenate of lead which consists in first causing a reaction between lead oxid and a lead nitrate solution of specific gravity 1.02 in the pro ortions of one thousand pounds of lead oxi and nine hundred gallons of lead nitrate solution, and subsequently adding thereto suflicient arsenic acid to combine with the basic lead 'ni- 1 f lead, which consists in reacting upon basic lead nitrate and an excess of lead oxid with arsenic acid, introducing sufiicient lead oxid in excess of the combining quantity with the lead nitrate to neutralize the nitric acid roduced in the reaction between the basic ead nitrate and the arsenic acid, thereby preventing theultirnate redissolving of the arsenate of lead formed, and simultaneously producing nitrate of lead to be subsequently used in react'ng with more oxid of lead the excess of lead oxid being suflicient in amount.

Signed at the city, count and .Siiigter of New York this 31stday of anuar GEORGE am has.

WILLIAM C. PIVER.

It is hereby certified that in Letters Patent No. 1,296,557, granted March 4, 1919, upon the application of George R. Riches and William C. Piver, of Hoboken, New Jersey, for an improvement. in Processes of Making Arsenate of Lead," errors appear in the printed specification requiring correction as follows: Page 2, line 74, claim 8, beginning with the word "introducing strike out all to and including the word nitrate, line 76, and insert the words the excess of lead oxid wed being eujiciem in amount; same page and claim, line 82, commencing with the word "the," strike out all to the end of the claim and insert a comma and the worde and eliminating fi-ce acid at the completion of the radio; and that, the'said Letters Patent should be reed with these corrections therein that the same may conform to the record of the case in the Patent Ofliee.

Signed and sealed this 15th day of April, A. D., 1919.

F. w. H. CLAY, Acting Oommiu-ioner of Patents.

[sun] Cl. 23 l 3. 

